Stress and displacement of surrounding rock with shallow twin-parallel tunnels

The derivation of an explicit analytical solution is presented to calculate the stress and displacement fields due to the excavation of twin-parallel tunnels in a homogeneous elastic half plane. The solution, which is achieved successfully by the program with computer, is based on the advantage of the complex variables for solving the problems of the plane with hole and the simple repeated calculation steps of alternating method. The calculation precision is discussed from three different aspects of the approximation accuracy of additional surface force, the convergence degree of the iterative calculation and the displacement of tunnel boundary. Furthermore, the method is applied to a practical tunnel engineering. It is found that the calculated results of the surface displacements caused by excavation of a tunnel and twin tunnels agree with the measured results. The discrepancy of the maximum surface displacements between the analytical solution and the field measurement is less than 5%.